CN105634300A - Piezoelectric energy collection rectifier for open-circuit type optimization of turnover time - Google Patents

Abstract

The invention discloses a piezoelectric energy collection rectifier for open-circuit type optimization of turnover time. The piezoelectric energy collection rectifier comprises two active diodes, two switches, an inductor and a peak detection and digital circuit control module, wherein a pair of active diodes carries out complementary conduction/stop operation; once one diode detects a zero crossing point flowing through a current from a positive electrode to a negative electrode, the diode is turned off and opposite the other diode is turned on; each active diode outputs a corresponding on-off state signal; the peak detection and digital circuit control module receives the on-off state signal of each active diode, detects a voltage peak of a cathode of the active diode and outputs a pulse signal of the optimized pulse width; the two switches receive the pulse signal of the peak detection and digital circuit control module and carry out on/off operation; and the inductor is connected with a piezoelectric device in series, and is connected to an input end of the rectifier. Under the control of the peak detection and digital circuit control module, the capacitor voltage of the piezoelectric device is optimally turned over; and meanwhile, the energy is transmitted to a load.

Description

A kind of open type optimizes the piezoelectric energy of flip-flop transition and gathers commutator

Technical field

The invention mainly relates to mechanical energy and be converted to the field of electric energy, refer in particular to a kind of open type and optimize the piezoelectric energy collection commutator of flip-flop transition.

Background technology

Energy collecting device based on piezoelectric type overarm arm configuration has the advantages such as low cost, high power density, high scalability because of it, makes it be highly suitable for miniaturization vibrational energy acquisition system. But the obtainable power of miniaturization energy collecting system is non-normally low, it is generally below 1 milliwatt, and the loss caused at energy transport reduce further the net energy of load. Therefore, the circuit design of a low-power consumption is essential. Further, since the voltage from piezoelectric transducer output is alternating current, and load needs a galvanic current pressure, therefore also needs to an exchange and turns the commutator of direct current.

What Fig. 1 represented is the piezoelectric energy Acquisition Circuit of a typical use full-bridge rectifier, the forward voltage that in this circuit, passive diode is intrinsic drops and is about 0.7 volt, too much conduction loss can be introduced when transmitting piezoelectricity end energy to load, and in order to transfer energy to load, piezoelectricity terminal voltage difference have to be larger than the sum that two diode forward voltages drop, namely about 1.4 volts, thus limiting the application at small-sized piezoelectric energy acquisition of this circuit.

On the other hand, as it is shown in figure 1, because piezoelectric device output reactance presents big capacitive, when every half vibration period piezoelectricity terminal voltage upset, electric charge all can be had to be wasted in the charge and discharge point process to piezoelectric transducer electric capacity. In order to avoid electric charge is wasted, extract the energy from piezoelectricity end more, there has been proposed various nonlinear method. What Fig. 2 represented is a kind of typical series inductance synchro switch energy acquisition circuit, also referred to as series inductance switch energy acquisition technique. This technology uses the inductance of a series connection and switchs the input connected as full-bridge rectifier with piezoelectric transducer. Switch cut-off within the most of the time of vibration period, piezoelectric charge is gathered on electric capacity and forms the voltage slowly risen, once reach voltage peak, namely during piezoelectricity end output current zero-crossing point, switch of short duration conducting, the part energy being stored on electric capacity is passed to load end, and another part energy returns piezoelectricity end, and forms the voltage of upset in piezoelectric capacitance. Once remaining energy all returns electric capacity, switch ends again, and the reverse current of transmitter to electric capacity reverse charging, and repeats said process in lower half vibration period.

Although the problem that the circuit shown in Fig. 2 solves electric charge waste, but it use passive diode, add conduction loss, limit piezoelectricity end output voltage amplitude, and the ON time of switch is subject to the impact of inductance, piezoelectricity end electric capacity, even load, the accurately control of conducting duration needs extra artificial adjustment, and inappropriate switch conduction duration will be substantially reduced the extraction efficiency of commutator. Considering these problems, this circuit is not suitable for small-sized piezoelectric energy collection.

Summary of the invention

For solving above-mentioned technical problem, the present invention proposes a kind of open type and optimizes the piezoelectric energy collection commutator of flip-flop transition. solution is: a kind of open type optimizes the piezoelectric energy of flip-flop transition and gathers commutator. this commutator includes two active diodes with Enable Pin, it is connected to detect the electric current that flows through zero crossing from positive to negative, once current zero-crossing point, turn off this diode, enable active diode on the other side, changing One-position switch status signal, this signal is sent to the input of Digital Circuit Control module and the Enable Pin of relative diode as the output of active diode, and a peakvalue's checking and Digital Circuit Control module, it is coupled to receive the switch state signal of described active diode, and detect the voltage peak now with source diode cathode terminal, or the voltage peak at piezoelectric device two ends, the pulse signal of output optimization pulsewidth is sent to the input of switch and controls end, and two switches, it is connected to the outfan of Digital Circuit Control module to receive described peakvalue's checking and the pulse signal of Digital Circuit Control module, completes conduction and cut-off operation, and an inductance, its connect with piezoelectric device with piezoelectric device export current zero-crossing point time with piezoelectricity end electric capacity, load collectively forms a resonator cavity, while Load transportation energy, help to overturn the capacitance voltage of piezoelectric device, this inductance one end is connected with piezoelectric device one end, the other end of inductance is connected with the negative electrode of described active diode and one end of a switch, the other end of piezoelectric device is connected with the negative electrode of another described active diode and one end of another switch respectively, the other end of two switches is connected to load, the anode of two active diodes is connected to ground.

The piezoelectric energy optimizing flip-flop transition that the present invention proposes gathers commutator, and advantage is in that:

1. series inductance synchro switch energy acquisition technology is incorporated in full-bridge rectifier structure, relative to conventional serial inductance synchro switch energy acquisition technology, decrease a switch element, reduce hardware cost.

2. use active diode and switch rather than passive diode in commutator to greatly reduce forward voltage and drop.

3. can automatically detect inductive current zero crossing, it is achieved Zero Current Switch, and synchro switch has a switch conduction duration optimized.

4. there is the Digital Circuit Control module of a simple low-power consumption, which reducing the extra power consumption using inductance synchro switch energy acquisition technology to bring, thus adding load end or the net energy of energy storage end.

Accompanying drawing explanation

Fig. 1 typically uses the piezoelectric energy Acquisition Circuit of full-bridge rectifier and corresponding node waveform diagram;

Fig. 2 typically uses the piezoelectric energy Acquisition Circuit of series inductance synchro switch energy acquisition technology and corresponding node waveform diagram;

Fig. 3 is the piezoelectric energy collection commutator that open type disclosed by the invention optimizes flip-flop transition;

Fig. 4 is the waveform time diagram of commutator key event disclosed by the invention;

Detailed description of the invention

Below in conjunction with accompanying drawing and be embodied as the present invention is described in further details.

As shown in Figure 1, Figure 2 and Figure 3, piezoelectric transducer is equivalent to a circuit model, and this circuit model includes a current source i of parallel connection_P, a resistance R_PWith an electric capacity C_P. Assume that current source can be expressed as

i_P=I_Psin(2��f_Pt)(1)

Wherein current amplitude I_PRelevant to the acceleration magnitude of vibration source, f_PThe frequency of vibration of corresponding vibration source. Additionally, because resistance R_PValue very big in million ranks, so can ignore in analysis, and assume load capacitance C_LValue very big so that V_RECTA galvanic current pressure can be regarded as.

Fig. 3 show the commutator of the present invention, and its basic operation logic is referred to Fig. 4, and before the t3 moment, diode D1 is opened, and D2 is turned off, and S1 and S2 ends, B point voltage V_BDue to i_PCharging is gradually increasing, when it rises to peak value, namely i_PWhen near zero-crossing point from positive to negative, switch S2 conducting, one through path A-B-V_RECTThe resonator cavity of-C-D is formed. It is stored in electric capacity C_PIn part energy by this path transmission to load, another part is in inductance L, and then the energy in inductance is returned to electric capacity C_PIn, and the voltage of a upset is produced at its two ends. Owing to now D1 is arranged in resonance loop, electric current can only along A �� B �� V_RECTThe direction flowing of �� C �� D; When all energy in inductance pass C back_PAfter, capacitance voltage switching process terminates automatically. Once complete upset in the t4 moment, D1 is turned off, and S2 ends again, and D2 is opened. Reverse current i_PElectric capacity is charged, V_DOr V_AVoltage is gradually increasing until detecting that D or A point voltage reaches peak value. Same operation principle, at i_PThe negative half-cycle similar operation operation when repeating its positive half period. And repeat whole process at next current cycle.

The output of the typical commutator shown in Fig. 1 can be expressed as

$P_{L,FB}=2V_{RECT}(\frac{I_P}{\mathrm{\π}}-2C_P{V}_{RECT}{f}_P-4C_P{V}_D{f}_P)---\left(2\right)$

Wherein V_DForward voltage for passive diode drops. Through type (2) can show that the obtainable peak power of load end is

$P_{L,FB}\left(max\right)=C_P{f}_P{(\frac{I_P}{2{\mathrm{\πf}}_P{C}_P}-2V_D)}^2---\left(3\right)$

Now $V_{RECT}=\frac{I_P}{4{\mathrm{\πf}}_P{C}_P}-V_D.$

And the commutator of the present invention is because adopting active diode and switch, forward voltage drops and is negligible. The switch of short duration Guan Bi of S1 or S2, is stored in electric capacity C every time_PPart energy be passed to load end, another part energy be used for overturn electric capacity C_PVoltage. Other times section, switch S1 and S2 ends, and piezoelectricity end disconnects with load end, and formula (4) gives voltage V within the time period_MWith V_mBetween relation, with reference to Fig. 3, V_MWith V_mCorrespond respectively to the voltage that rollover event is forward and backward.

$\left|V_M\right|=\left|V_m\right|+\frac{2I_P}{{\mathrm{\ωC}}_P}---\left(4\right)$

Upset every time, the energy of piezoelectricity input output is

$V_{RECT}{\∫}_0^{T/2}Idt=V_{RECT}{C}_p(V_M+V_m)=\frac{\mathrm{\π}}{R_L\mathrm{\ω}}{V}_{RECT}^2---\left(5\right)$

It is the ratio resetting voltage difference with turnover voltage difference with reference to Fig. 4, definition ��,

$\mathrm{\η}=\frac{\left|V_m\right|+V_{RECT}}{\left|V_M\right|-V_{RECT}}---\left(6\right)$

The output DC voltage V of load end can be obtained by (4), (5) and (6)_RECTFor

$V_{RECT}=\frac{2R_L{I}_p(1+\mathrm{\η})}{\mathrm{\π}(1-\mathrm{\η})+2R_L{C}_p\mathrm{\ω}(1+\mathrm{\η})}---\left(7\right)$

Because its output can be expressed as

$P_L=\frac{V_{RECT}^2}{R_L}---\left(8\right)$

To formula (8) derivation, can obtain maximum output is

$P_{L,SER}\left(max\right)=\frac{1+\mathrm{\η}}{1-\mathrm{\η}}\·\frac{I_p^2}{2{\mathrm{\πC}}_p\mathrm{\ω}}---\left(9\right)$

Now optimum load resistance and optimum output DC voltage are respectively

$R_{L,OPT}=\frac{1-\mathrm{\η}}{1+\mathrm{\η}}\·\frac{\mathrm{\π}}{2C_p\mathrm{\ω}},V_{RECT,OPT}=\frac{I_p}{2{\mathrm{\ωC}}_p}---\left(10\right)$

Adopt the parameter such as I of a reasonable set_P=100 �� A, f_P=100Hz, C_P=20nF, ��=0.7, V_D=0.7 substitutes into formula (3) and formula (9). Diode full-bridge peak power output is 86 �� W, and the peak power output adopting the present invention is 717 �� W, is about 8 times of diode full-bridge peak power output.

In sum, commutator disclosed by the invention has the circuit structure of a kind of novelty, this structure has incorporated series inductance synchro switch energy acquisition technology, and there is a simple control circuit to control the capacitance voltage optimization upset of piezoelectric energy collector, plus the use of active diode and switch, finally effectively increase load end or the net energy of energy storage end.

Although the embodiment of the relatively limited quantity of the present invention is described, but benefits from and it should be appreciated by those skilled in the art that consequent numerous modifications and variations disclosed in this. Claims are intended to belong to these type of modifications and variations of true spirit of the present invention and scope.

Claims (4)

1. open type optimizes the piezoelectric energy collection commutator of flip-flop transition, including:

Two active diodes with Enable Pin, it is connected to detect the electric current that flows through zero crossing from positive to negative, once current zero-crossing point, turn off this diode, enable active diode on the other side, and changing the One-position switch status signal of its output, this signal is sent to the input of Digital Circuit Control module and the Enable Pin of relative diode as the output of active diode; And

One peakvalue's checking and Digital Circuit Control module, it is coupled to receive the switch state signal of described active diode, and detect the voltage peak now with source diode cathode terminal, or the voltage peak at piezoelectric device two ends, the pulse signal of output optimization pulsewidth is sent to the input of switch and controls end; And

Two switches, it is connected to the outfan of Digital Circuit Control module to receive described peakvalue's checking and the pulse signal of Digital Circuit Control module, completes conduction and cut-off operation; And

One inductance, its connect with piezoelectric device with piezoelectric device export current zero-crossing point time with piezoelectricity end electric capacity, load collectively forms a resonator cavity, while Load transportation energy, help to overturn the capacitance voltage of piezoelectric device, this inductance one end is connected with piezoelectric device one end, the other end of inductance is connected with the negative electrode of described active diode and one end of a switch, the other end of piezoelectric device is connected with the negative electrode of another described active diode and one end of another switch, the other end of two switches is connected to load, the anode of two active diodes is connected to ground.

2. active diode as claimed in claim 1 is the diode of a pair complementary conduction and cut-off, when its cathode voltage is higher than anode, active diode ends, switch state signal is output as a high level, relative active diode conducting, when cathode voltage is lower than anode, active diode turns on, switch state signal is output as a low level, relative active diode cut-off.

3. switching as claimed in claim 1, before peakvalue's checking and digital circuit blocks detect voltage peak, two switches all end, once voltage peak be detected, and a switch conduction corresponding with this voltage.

4. peakvalue's checking as claimed in claim 1 and Digital Circuit Control module, when voltage peak being detected, the level upset of the output signal of its correspondence, a corresponding switch conduction, active diode switch state signal automatic turning subsequently, the change of this signal is once detected, and output is flipped back to former level, switch cut-off again.